1. Field of the Invention
The present invention relates to a check valve and, more particularly, to a low pressure drop hydraulic or pneumatic check valve.
2. Description of the Related Art
Aerospace pneumatic check valves, among other types of check valves, are typically required to meet stringent weight and space constraint requirements, while generating the lowest possible pressure drop for a particular flow rate and operating pressure. Many aerospace applications restrict the envelope size of the check valve to the space available or remaining on an aircraft after all of the major aircraft components have been positioned and installed. If, for example, a relatively small, lightweight check valve is required in a given aircraft installation, a check valve manufacturer is typically required to use a single piece housing for the body of the check valve to minimize envelop size and weight. Although satisfactory for reducing size and weight, a single piece housing undesirably restricts the size of the internal check valve components to the size of the housing's inlet and outlet ports through which these components must pass during assembly.
If, on the other hand, a low pressure drop check valve is required in a given aircraft installation, then the aircraft manufacturer typically demands the lowest pressure drop obtainable regardless of envelope size or weight. Since the pressure drop for a given flow rate is inversely proportional to the size of the cross-sectional area of the flow path, a check valve's inlet and outlet diameters often dictate the amount of pressure drop. In addition to the inlet and outlet diameters, other factors contribute to the pressure drop of a hydraulic or pneumatic check valve, including without limitation, fluid drag along the walls and surfaces of the check valve, change in direction of flow through the check valve, division of a single flow path into several flow paths and corresponding merger of several flow paths into a single flow path, acceleration and deceleration of the fluid flow stream, presence of eddy currents in the flow stream, and the energy required to hold a poppet valve open against a biasing spring force. Any check valve design that limits or reduces the effect of these factors will reduce the pressure drop for a given fluid, at a given flow rate and at a given pressure.
In light of these and other considerations, check valve designers balance the requirements for lower weight, smaller envelope size and lower pressure drop in their designs, while reducing the cost to manufacture. Since, size and weight of a check valve are generally inversely proportional to its pressure drop, prior art check valve designs typically compromise one feature for another. For these and other reasons, an improved check valve is desired that overcomes limitations of the prior art.